Height is an example of gene but short is an example of what

Each hereditary trait corresponds to

Which of the following must be true for a fossil organism to be useful as an index fossil? a. the fossil organism must be widespread geographically. b. the fossil organism must be abundant. c. the fossil organism must be limited to a short span of geologic time. d. all of the above.

The big bang theory suggest that the universe is about - 300 million years old - 4.6 billion years old - 30 billion years old - 13 billion years old